Utilization of virtual non-contrast images derived from dual-energy CT in evaluation of biliary stone disease: Virtual non-contrast image can replace true non-contrast image regarding biliary stone detection

Objectives: To compare the virtual non-contrast (VNC) images acquired through dual-energy computed tomography (DECT) with the true non-contrast (TNC) images in the detection of biliary stones and to calculate dose reduction by replacing TNC images with VNC images. Methods: Between March 2017 and April 2018, we retrospectively enrolled 75 patients with suspicious biliary disease who underwent dual-source DECT and surgery and/or endoscopic intervention within 2 months from the CT. Biliary stones were present in 45 patients. The sensitivity and specificity for detecting gallstone and common bile duct (CBD) stone were compared between the VNC and TNC using McNemar test. In addition, the possible reduction in radiation dose was calculated. Results: In our study, 37 patients had gallstones, 2 had CBD stones, and 6 had both gallstone and CBD stones. For detection of gallstones, the sensitivity and specificity were 90.7% (39/43) and 87.5% (28/32), respectively, for the TNC images, and 88.4% (38/43) and 90.6% (29/32), respectively, for the VNC images. With respect to CBD stones, the sensitivity and specificity were 87.5% (7/8) and 98.5% (66/67), respectively, for the TNC images, and 75.0% (6/8) and 100% (67/67), respectively, for the VNC images. There was no significant difference in the sensitivity and specificity between each image set (P > 0.05). The radiation dose reduction of 22.4 +/- 1.3% is expected by omitting TNC images. Conclusions: The VNC images derived from DECT were comparable to the TNC images for the detection of biliary stones and may replace the TNC images to reduce radiation dose.